Low profile fusion cage and insertion set

ABSTRACT

A bone fusion implant system including a first implant body having substantially flat top and bottom surfaces for engaging opposing vertebrae and a side wall extending between the top and bottom surfaces, the side wall including a concave recess and a second implant body having substantially flat top and bottom surfaces for engaging the opposing vertebrae and a side wall extending between the top and bottom surfaces thereof, the side wall of the second implant including an arcuate portion adapted to be received within the concave recess for enabling the first and second implant bodies to be positioned in nested side-by-side relation between the opposing vertebrae.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 10/338,463, filed Jan. 8, 2003, now allowed, which is adivisional of U.S. patent application Ser. No. 09/545,320, filed Apr. 7,2000, now U.S. Pat. No. 6,783,545, which claims benefit of U.S.Provisional Application No. 60/128,113, filed Apr. 7, 1999. Thedisclosures of the '463, '320 and '113 applications are herebyincorporated by reference herein.

BACKGROUND OF THE INVENTION

The present application relates to a low profile fusion cage and aninsertion set for the low profile fusion cage.

Known spinal implants, such as those used for vertebral fusion, areoften used in pairs to provide adequate, evenly distributed support andfusion inducement. Because of limited space for implantation and forsurgical maneuvering, it is sometimes difficult or unfeasible toimplement a pair of implants that otherwise have desirable dimensionsand attributes. Certain existing implant designs are configured forclose, adjacent placement to other implants, but none achieve optimumperformance, versatility or ease of insertion.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an implant design,and associated instruments and methods, that provide optimumconfigurations for placement of adjacent implants in close proximitywith optimum performance. These objects and others are achieved throughthe present invention implant configuration and associated instrumentsand method.

In a preferred embodiment, a fusion implant according to the presentinvention is provided with a concave cut-away portion on acircumferential surface of an elongated implant. The concave portionaccommodates the outer contour of an adjacently placed implant having acorresponding concave surface. A novel dual tang distractor tool isprovided with two over-lapping cross-sectional configurations tofacilitate close insertion and placement of implants according to thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present disclosure are described hereinwith reference to the drawings wherein:

FIG. 1 is a perspective view of the fusion cage of the presentdisclosure;

FIG. 2 is a side view of the fusion cage of FIG. 1;

FIG. 3 a is a cross-sectional view of the fusion cage taken along linesB-B of FIG. 1;

FIG. 3 b is a cross-sectional view of the fusion cage as shown in FIG. 3a, with a conventional implant cage of similar view placed adjacentlythereto.

FIG. 4 is a perspective view of the tang retractor of the presentdisclosure;

FIG. 5 is a perspective view of the guide of the present disclosure;

FIG. 6 is a perspective view illustrating attachment of the guide to thetang retractor,

FIG. 7 is a perspective view of the plate of the impactor;

FIG. 8 is a front, perspective view of an alternative embodiment of thepresent invention; and

FIG. 9 is a front, perspective view of another alternative embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1-3 a illustrate perspective, side and end views of the lowprofile fusion cage (10) of the present invention. The present inventioncage (10) is of the type known commercially as the Ray TFC™ Fusion Cagecurrently marketed by Surgical Dynamics, Inc. The Ray TFC™ Fusion Cageis disclosed in commonly assigned U.S. Pat. No. 4,961,740, the contentsof which are incorporated herein by reference.

The fusion cage (10) disclosed herein can be implemented with anotherfusion cage to reduce the total amount of space occupied by twoconventional fusion cages placed side by side. The fusion cage (10) hasa helical thread (14) for facilitating insertion and securing of thecage (10) in a vertebral disc space. The thread (14) is carved out toform concave portions (16, 17) to reduce the profile of the thread. Asshown, the concave portions (16, 17) are preferably provided 180 degreesapart. If desired, only one concave portion is necessary to carry outthe present invention. It is possible, also, to provide more than twoconcave portions if desired. The concave portions (16, 17) allow two ormore cages (10, 11) to be placed close together as the radiused portionof one cage (11) is placed within the concave portion (17) of anadjacent cage (10), as shown in FIG. 3 b. As can be appreciated, thecombined width (transverse space) of the two low profile cages (10, 11)placed in this fashion is less than the combined width if twoconventional cages without at least one of them having a concave portionwere placed side by side.

FIGS. 4-7 b illustrate an insertion instrument set for fusion cagesaccording to the present invention. The instrument set includes a tangretractor (20), a guide (30) and an impactor (40) and impactor plate(41). The tang retractor (20) includes a pair of spaced apart tangs (21)which are dimensioned and configured as wedges at the distal end forinsertion into and distraction of the disc space. The configuration ofthe tangs (21) and the manner in which they distract the disc space isdescribed in pending U.S. patent application Ser. No. 08/889,661, filedJul. 8, 1997, the contents of which are incorporated herein byreference.

The tang retractor (20) includes a pair of proximally extending slottedtabs (22) for mounting the tabs (42) of the impactor plate (41) when theimpactor plate (41) is mounted to the proximal end of the distractor(20). The tabs (42) are inserted into the slots (23) of the tabs (22) tomount the impactor plate (41) and the elongated integral impactor (40),which is connected to the impactor plate (41) by threads (43, 45), tothe tang retractor (20). The impactor (40) can then be impacted ortapped at its proximal end (47) by a suitable tool, such as a hammer, toinsert the tang (21) into a vertebral space. After insertion, the tabs(42) are slid out of engagement with slots (23) to separate and removethe impactor (40) and impactor plate (41), leaving the tang retractor(20) in place with the tangs (21) inserted in the vertebral space.

The guide (30) is then attached to tang retractor (20) by inserting thedistal end pin (32) into the longitudinal slot (25) of the retractor(20). The distal end pin (32) is seated within the slot (25) 50 that theguide (30) can be pivoted, about the pin (32), with respect to the fixedtang retractor (20) between alignment with each of the two openings (26,27) of the tang retractor (20), respectively. Each of the openings (26,27) is configured to receive a fusion cage along with a conventionalcage insertion tool (not shown). The guide (30) is rotated about pin(32) 50 that its axial bore (34) is aligned with one of the openings(26, 27) of the tang retractor (20) during hole preparation through arespective one of the openings. Suitable tools, such as those describedin the aforementioned application Ser. No. 08/889,661, are insertedthrough the bore (34) to prepare the space for fusion cage insertion.Fusion cages such as the type of the present invention, are theninserted via an elongated insertion tool through the bore (34) and therespective tang retractor opening (26, 27) for placement within thevertebral space. Each cage is placed so that one of the concave portions(16, 17) faces the adjacent opening or bore in the vertebral space. Theguide (30) is subsequently rotated so that axial bore (34) is alignedwith the other opening (26, 27) in the retractor 20. Another fusioncage, either with or without concave portions, is inserted in a similarmanner as described above so that its outer circumferential portion fitswithin the concave portion (16, 17) of the first-inserted fusion cage.

It is contemplated that an interlocking device (33) be provided toretain the guide (30) in each of its two aligned positions relative tothe tang retractor (20) during site preparation and insertion of afusion cage therethrough.

Alternate embodiments of the present invention, such as those shown inFIGS. 8-9, include variously configured implant bodies having-a concaveportion to facilitate close, adjacent placement with additional implantbodies. For instance, the implant body (100) in FIG. 8 is a half-ovalhaving a central opening (102) to facilitate bone fusion, and a concaveside wall (104) configured to matingly receive a circumferential, convexwall (106) of an adjacent, oval implant (108). The implant body (200) ofFIG. 9, is generally cylindrical and has a concave channel (202) alignedgenerally perpendicularly to a longitudinal axis running between openends (204, 206).

It can be appreciated that the tang retractor (20) having a lengthapproximately equal to its width increases visibility as well as enablesthe user to more easily remove extraneous disc tissue because of theincreased mobility of instruments, e.g. rongeurs, inserted through theretractor 20. While this is the preferred embodiment, the length of theretractor (20) may be varied as desired to achieve different advantages.

While the preferred embodiment has been disclosed herein, it isunderstood and contemplated that modifications and variations may beemployed without departing from the scope of the present invention.

1. A bone fusion implant system comprising: a first implant body havingsubstantially flat top and bottom surfaces for engaging opposingvertebrae and a side wall extending between said top and bottomsurfaces, said side wall including a concave recess; a second implantbody having substantially flat top and bottom surfaces for engaging theopposing vertebrae and a side wall extending between said top and bottomsurfaces thereof, said side wall of said second implant including anarcuate portion adapted to be received within said concave recess forenabling said first and second implant bodies to be positioned in nestedside-by-side relation between said opposing vertebrae.